Marathonissi is a small uninhabited island in the bay of Laganas. It is also known as Turtle Island. You can reach Marathonisi if you take any of the boats on the beach of Laganas and Keri. There are no stores on this beach, you should take your need.
Marathonisi beach and the whole area of Laganas bay is one of the most important shelters for the endangered species of Caretta-caretta in Greece.